English verb conjugation
MUST RIFF

Regular verb: riff - riffed - riffed

Affirmation

Simple form	V-ing form
I must riff you must riff he must riff we must riff you must riff they must riff	I must be riffing you must be riffing he must be riffing we must be riffing you must be riffing they must be riffing
Perfect	V-ing perfect
I must have riffed you must have riffed he must have riffed we must have riffed you must have riffed they must have riffed	I must have been riffing you must have been riffing he must have been riffing we must have been riffing you must have been riffing they must have been riffing

Negation

Simple form	V-ing form
I mustn't riff you mustn't riff he mustn't riff we mustn't riff you mustn't riff they mustn't riff	I mustn't be riffing you mustn't be riffing he mustn't be riffing we mustn't be riffing you mustn't be riffing they mustn't be riffing
Perfect	V-ing perfect
I mustn't have riffed you mustn't have riffed he mustn't have riffed we mustn't have riffed you mustn't have riffed they mustn't have riffed	I mustn't have been riffing you mustn't have been riffing he mustn't have been riffing we mustn't have been riffing you mustn't have been riffing they mustn't have been riffing

Interrogative form

Simple form	V-ing form
must I riff? must you riff? must he riff? must we riff? must you riff? must they riff?	must I be riffing? must you be riffing? must he be riffing? must we be riffing? must you be riffing? must they be riffing?
Perfect	V-ing perfect
must I have riffed? must you have riffed? must he have riffed? must we have riffed? must you have riffed? must they have riffed?	must I have been riffing? must you have been riffing? must he have been riffing? must we have been riffing? must you have been riffing? must they have been riffing?

Interro-negative form

Simple form	V-ing form
mustn't I riff? mustn't you riff? mustn't he riff? mustn't we riff? mustn't you riff? mustn't they riff?	mustn't I be riffing? mustn't you be riffing? mustn't he be riffing? mustn't we be riffing? mustn't you be riffing? mustn't they be riffing?
Perfect	V-ing perfect
mustn't I have riffed? mustn't you have riffed? mustn't he have riffed? mustn't we have riffed? mustn't you have riffed? mustn't they have riffed?	mustn't I have been riffing? mustn't you have been riffing? mustn't he have been riffing? mustn't we have been riffing? mustn't you have been riffing? mustn't they have been riffing?